Steps to reproduce:
1. Download attached project
2. Open it. Say no to script upgrade.
3. Open player settings of Windows Store Apps, lock the Inspector.
4. Right click on one of the old scripts and select to upgrade them.
5. Click through different Player Settings of Windows Store Platform. Exceptions are thrown.

GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced)

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Metro.MetroSettingsEditorExtension.ImageField (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, Single kLabelMinWidth, Single kLabelMaxWidth, Single kLabelMinHeight, Single kLabelMaxHeight, Int32 imageWidth, Int32 imageHeight) (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/MetroSettingsEditorExtension.cs:433)
UnityEditor.Metro.MetroSettingsEditorExtension.MetroLogoSection (Single kLabelMinWidth, Single kLabelMaxWidth, Single kLabelMinHeight, Single kLabelMaxHeight) (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/MetroSettingsEditorExtension.cs:467)
UnityEditor.Metro.MetroSettingsEditorExtension.IconSectionGUI () (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/MetroSettingsEditorExtension.cs:650)
UnityEditor.PlayerSettingsEditor.IconSectionGUI (BuildTargetGroup targetGroup, ISettingEditorExtension settingsExtension) (at C:/buildslave/unity/build/Editor/Mono/Inspector/PlayerSettingsEditor.cs:623)
UnityEditor.PlayerSettingsEditor.OnInspectorGUI () (at C:/buildslave/unity/build/Editor/Mono/Inspector/PlayerSettingsEditor.cs:439)
UnityEditor.InspectorWindow.DrawEditor (UnityEditor.Editor editor, Int32 editorIndex, Boolean forceDirty, System.Boolean& showImportedObjectBarNext, UnityEngine.Rect& importedObjectBarRect, Boolean eyeDropperDirty) (at C:/buildslave/unity/build/Editor/Mono/Inspector/InspectorWindow.cs:1118)
UnityEditor.DockArea:OnGUI()